The present invention relates generally to apparatus for removing from a moving workpiece a mixture of blasting media and cleaning residues accumulated on the surface of workpieces treated with blasting media and is more particularly adapted for use with workpieces having relatively larger horizontal surfaces. The invention involves operation by removal of the mixture by conveyance thereof in directions transverse to the feed direction of the workpiece and additionally by blasting.
An arrangement of the type to which the present invention relates to known from German DOS No. 652,005. In this prior art device, the entire mixture for blasting media and cleaning residues accumulating on the workpiece is blown off by means of a blowoff mechanism into a tank which is arranged above the passage through which the workpiece travels. The mixture is here removed by a conveyer device which may be, for example a screw.
A disadvantage of prior art arrangements of this type is that the entire mixture accumulating upon the workpiece from the blasting treatment must be blown off by the blowoff device into a tank or receptacle which is arranged at a higher level. Thus, the material or mixture must be raised and this leads to a disproportionately high consumption of air and tends to require correspondingly higher power input demands.
A further prior art arrangement which is generally intended for the blasting treatment of plates and bands is known from U.S. Pat. No. 2,204,588. In this device, belt conveyers are arranged on both sides of a blasting jet in a blast chamber transverse to the feed direction of the workpiece and baffle plates operate the conduct rebounding blasting media to these conveyers. As a result, a part of the blasting media is removed laterally while still inside the blast chamber. Outside the blast chamber there are arranged blowoff nozzles which tend to have an acuminated form and which blow off the remaining blasting medium in both directions. A disadvantage of this prior art arrangement is that the conveyer belts arranged in the blast chamber are subject to excessive wear and that a relatively large amount of blasting medium is conveyed under the belt and out of the blast chamber while resting upon the plate and it must be removed with a relatively high amount of blowoff power.
Additionally, the blowoff nozzles having the acuminated form are poorly suited for application with larger plate widths since the required air consumption will increase disproportionately in such an arrangement.
The present invention is directed toward overcoming problems arising in arrangements of the aforementioned type and avoiding inconveniences attendant therewith whereby larger amounts of blasting media and cleaning residues can be removed safely and economically from workpieces having relatively large horizontal surfaces.